The long-term objective of this project is to develop appropriate diagnostic assays for bioterrorism attacks. A well coordinated and executed attack could kill hundreds of thousands to millions. Effective diagnostics will be crucial to minimizing morbidity and mortality from such an attack, as well as maintaining social order. These diagnostics must be rapid, easy to use, inexpensive, very sensitive, and very specific. Multiplexed tests (i.e., those that test for multiple targets) and low waste generation are also attractive capabilities for these diagnostics. Our near-term objective is to test the feasibility of a new diagnostic approach that should significantly outperform existing diagnostics in terms of speed, sensitivity, and simplicity of use. This assay is based on upconverting chelates in a homogeneous assay format. Upconverting chelates are a novel reporter SRI International (SRI) has invented that comprises a lanthanide (rare earth) ion in a chelating ligand. When excited with near infrared light, they upconvert, emitting light at visible wavelengths. These reporters have no autofluorescent background, do not photobleach, and have good properties for multiplexing. Because the assay is homogeneous, very little sample preparation is required, enabling rapid analysis. We propose a 2-year R21 project to prove the feasibility of this assay. As a test target we will use influenza virus strain PR8. Our specific aims in this work are to: (1) build a simple optical apparatus for detecting surface-enhanced upconverting chelate signals; (2) prove and optimize the homogeneous assay concept; (3) prove and optimize the assay for hemagglutinin protein; and (4) prove and optimize the assay for influenza virus. This work will combine the efforts of optical physicists, chemists, immunologists, and a virologist.